Advanced Materials Research Vols. 1065-1069

Abstract: High altitude cold regions tunnel construction environment is the key factor of tunnel construction progress, also relates to the technical personnel's health, this paper analyzes several key factors of restricting the construction environment, the field test of dust and CO several important indexes such as the maximum value, it is concluded that high altitude cold regions tunnel construction environment is relatively poor, dust and CO value beyond the standard requirements. Based on this, puts forward the measures to control the environment of high altitude cold regions tunnel construction for reference by the similar projects.

Abstract: During the shallow-buried tunnel excavation, the formation will be affected and the nearby buildings will be caused fracture. By using three dimensional software MIDAS/GTS, the interactions among structures-soil-tunnel system is considered in this paper, and the working condition of shallow-buried underground excavation is simulated in the independent foundation of frame structures. It is indicated that building will tilt to the side of tunnel as the horizontal distance L between building and tunnels is increasing, after reaching certain distance, the influence to the building tends to little, at the same time, the maximum first principal stress P₁ and maximum deformation rate E₁ show a trend of decrease. When the kind of soil is worse, the settlement and non-uniform settlement of buildings increase, meanwhile P₁ and E₁ increase. With the increasing story of the framework, the settlement of building is nearly not affected, and P₁ and E₁ decrease slightly.

Abstract: This study simulated the condition of below-wall raft foundation supported masonry structure perpendicularly penetrated by shallow-buried and mining tunnelling using 3D MIDAS/GTS software with consideration of the coaction of structure, ground and tunnel. The load and deformation patterns of structure before and after the penetration of tunnelling excavation face were evaluated. Results from the study showed that: when the horizontal distance between the central axis of the structure and the axis of the tunnel L=0 m, the settlement of the structure increased before and after the penetration of tunnel through the masonry structure, and the settlement became stable after the tunnel passed through a certain distance (approximately 2.4 times of the thickness of ground cover); the structure settled overall and the difference of settlement was relatively small; the maximum first principal stress P₁ and the maximum deformation rate E₁ showed an overall increasing trend. With the increase of L from 0, inclination of the structure towards the tunnel was witnessed, the settlement of foundation appeared to be linearly distributed and the inclination rate of foundation first increased then reduced; P₁ showed a decreasing trend and E₁ first reduced, then increased and decreased again.

Abstract: Passing through the inland river the tunnel generally lead to overburden small thickness of overlying soil, the disturbance effect of shallow soil here is very large. So the research of the thickness of the overlying soil is the key to solve the engineering problems. The existing calculation formula of the thickness of covering soil only considering the static state after construction, does not take into account the grouting pressure to overlying soil disturbance during construction. Based on the existing thickness calculation formula, this paper attempts to get a new modified computational formula which take the grouting pressure into consideration, and puts forward the reasonable improvement according to different parameters.

Abstract: Ground Penetrating Radar is a method using high frequency impulse electromagnetic wave to detect underground media distribution. It has been gradually widely used as it has the advantage of high accuracy, fast and nondestructive respecting to the conventional method such as visual measurement and confirmation with drilling hole. In the tunnel construction process, it is easy occurred that the quality problem of insufficient lining thickness, the distance of steel arch centering too large and the concrete disengaging. The work achieved in this paper based on the project of LongSheng tunnel and its conclusion and suggestion has important practical engineering significance.

Abstract: Guangzhou Metro Line 6 the 8th tender Tianhe Station tunnel shielding meet hole body fissure water is abundant, tunnel soil mass disintegrates easily when water permeate, consolidating with end-advancing horizontal grouting technique. By reasonable choice construction equipment, drilling location, double liquid grouting parameters to control the construction process, enhance process monitoring, get a good reinforcement effect; analyzed the prospects of the construction method.

Abstract: Setting of insulation layer is widely recognized to prevent frost damage for tunnels constructed in cold region. Optimization design of insulation layers, however, still need deeply investigate. In this paper, taking Houanshan tunnel as example, two-dimensional finite element analysis on the optimization design of insulation layers has been carried out by ABAQUS. The tunnel temperature fields due to various thickness and length of insulation layer are numerically analyzed. It shows that ,1)4.85°C increased at backside of insulation layer with thickness of 5cm, while 5.8°C increased for thickness of 7cm;2) frozen depth of surrounding rock decrease with the increase of insulation layer thickness. The farther distance to tunnel portal, the smaller thickness of insulation layer required to prevent the surrounding rock from freezing;3)According to analysis, frost penetration length should be 450~500m before tunnel holing-through ,while 720m~830m after tunnel holing-through.

Abstract: Chamber earth pressure is one of the significant parameters during the Earth Pressure Balance (EPB) shield construction processing. The soil arching effect is existence when the tunnel depth is enough. It is significant to consider the influence of arching effect to analyze the pressure in soil chamber in shield tunneling. In this paper, the influence of arching effect is considered to calculate the chamber earth pressure. Firstly, the soil is supposed as loose media, and the necessary buried depth of producing arching affects is deduced according to the loose media theory. Then, based on the characteristic of proper arching axis, the equation and the height of proper arch are obtained. At last, the calculation formula of minimum chamber earth pressure of EPB shield tunnel is deduced which can consider the effect of arching effect.

Abstract: In the big cities, the shield undercrossing metro project has become critical to the safety of the metro, this paper takes the South-North Water Transfer Project shield under traverse Beijing certain subway project for construction background. It makes technical schemes comparison, analyses the deformation law of the existing subway structure and propoes protective measures to prevent the existing subway structure. The analysis showed the following conclusions: in shield undercrossing the metro project, in order to reduce disturbance on surrounding soils and the existing metro structure, we should take the necessary control measures such as grouting and determine the optimum shield parameters; the overall trend of the monitoring results accords well with numerical simulation results; The reason why the actual values and model calculation values has certain deviation is that it is difficult to consider shield parameters such as the pressure of shield thrust, pressures of grouting and so on in numerical simulation.

Abstract: The drilling and blasting method is popular for the construction of highway tunnel,which is easy to cause serious production safety accidents.Based on safety risk analysis of tunnel blasting construction,safety risk probability assessment index system of tunnel blasting construction was put forward,which consist of establishment of blasting scheme,belection of blasting equipment,and safety management,etc.Safety risk probability assessment model was constructed based on the fuzzy comprehensive evaluation,which are divided in five level.The risk matrix method was used to assess risk level of blasting construction,considering blasting construction risk probability and the consequence.Through the case on ChenJiagou tunnel in the province of Hebei proves the feasibility of evaluation method,and the corresponding risk control measurements were proposed.